The invention relates generally to film positioning systems for dental radiography procedures and, more particularly, to an aiming device that assures that a desired alignment is consistently and repeatedly maintained between an x-ray film, a dental arch, and an x-ray equipment.
Dental radiographic images are made using x-ray examination units for obtaining intraoral images of a patient's dental arch (e.g., teeth and gums). Such intraoral images are typically examined shortly after developing the x-ray film for the purpose of diagnosing the patient's oral health.
It is desired, however, to create a series of radiographic images over an extended period of time to better diagnose the patient's oral health. To support proper longitudinal analysis, it is important that the radiographic images are repeatedly aligned and taken with the same relative projection geometry.
Referring to FIG. 1, traditional dental radiography utilizes a rigid aiming device such as the device 10. The device 10 includes a bite block 14 located on a distal end 16 of a guiding rod 18. The bite block 14 includes a biting portion 20 and a film holder 22. A top surface of the biting portion 20 is parallel with the guiding rod 18 and perpendicular to the film holder 22.
Near a proximal end 24 of the guiding rod 18 is an aiming ring 26. The aiming ring 26 is circumferentially engageable about a x-ray position indicating device (or simply "cone") 28 for positioning the film holder 22 in a perpendicular orientation with respect to a line of sight 30 for x-rays emanating from the cone.
In operation, a patient places the bite block 14 inside his mouth 32 and compresses the biting portion 20 between corresponding upper and lower teeth 34. Ideally, a perpendicular orientation between the line of sight 30 and the film holder 22 will be maintained.
However, as is often the case, the film holder 22 provides discomfort because it contacts a surface of the mouth 32 (e.g., the roof of the mouth). When this occurs, the film holder 22 is often adjusted to a new position, such as is shown in phantom with film holder 22a. If the perpendicular orientation is to be maintained, then the biting portion 20 and the guiding rod 18 (and hence the aiming ring 26 and the line of site 30) must move to a new position, such as is shown in phantom with biting portion 20a and guiding rod 18a, respectively. If the biting portion 20a is flexibly connected to the film holder 22a and the guiding rod 18a, the orientation between the film holder 22a and the guiding rod 18a will most likely not be perpendicular. If the biting portion 20a is rigidly connected to the film holder 22a and the guiding rod 18a, the orientation may be perpendicular, but the exact position of the film holder 22a inside the mouth 32 will vary from one radiographic image to the next.
Therefore, what is needed is an aiming device that secures and maintains a desired orientation between the film holder and the guiding rod, yet accommodates different sized and shaped mouths and/or different projection geometries.